1. Field of the Invention
The present invention relates to engine analyzer apparatus used for testing internal combustion engines. In particular, the present invention relates to apparatus for measuring the condition of an ignition coil of an internal combustion engine.
2. Description of the Prior Art
A typical internal combustion engine used to power automobiles, trucks, and other land vehicles typically has several cylinders, and has an ignition system which includes a battery, an ignition coil, a condensor, a circuit interrupter (either breaker points or a solid state switching device), a distributor, and spark plugs for each of the cylinders. As the engine runs, the circuit interrupter periodically interrupts current flow through the primary winding of the ignition coil, thus inducing a high voltage output pulse which is supplied by the distributor to one of the spark plugs.
This type of ignition system requires periodic testing and maintenance in order to obtain the desired performance from the engine. It is necessary, on occasion, to determine whether the ignition coil is functioning properly and is providing the necessary output voltages to fire the various spark plugs. In the past, the testing of ignition coil condition has required the removal of a spark plug wire. This type of test, however, can be detrimental to the ignition system and dangerous to the person performing the test.
First, with improved components and materials used in modern vehicles, the length of time a spark plug wire is attached to a spark plug and the higher temperatures at which the engine is operating can cause the spark plug wire to become very difficult to remove without breaking. Second, since there is a tremendous amount of energy available in the secondary of the ignition system (especially in modern solid state ignition systems such as the General Motors HEI System), the opening of a spark plug wire may lead to a breakdown of the ignition voltage which may be damaging to the test equipment, or may cause carbon tracking in the distributor cap.